Directive 2008/50/EC of the European Parliament and of the CouncilShow full title

ANNEX XIII U.K. CRITICAL LEVELS FOR THE PROTECTION OF VEGETATION

Averaging period	Critical level	Margin of tolerance
Sulphur dioxide
Calendar year and winter (1 October to 31 March)	20 μg/m3	None
Oxides of nitrogen
Calendar year	30 μg/m3 NOx	None